So how about indirectly causing a chain reaction of multiple volcanos...

I am thinking of an earthquake on a large fault (say the cascadia fault) setting off multiple volcanos along the fault line. Or would a volcano going off always lower the stresses on connected faults?

I remember a cross country flight in late 90s (I think maybe a bit later) that had a crappy VHS player for the movie, the kind that had the jitter noise on the bottom. it was unwatchable, but they would not turn it off as the flight was billed as showing a movie.....

I actually have a set of commercial headphones that have that technology.

Yes the 3.5 jack has been a standard in personal electronics for years, and you are probably right about they reasons they designed the dual plug thing initially. but I think it was also, at least partially, what was submitted to the FAA and once it was approved it became the approved standard. Unlikely to change until they revisited entertainment systems. If there is no compelling (safety) reason they just don't redesign systems on passenger aircraft.

And the electronics certification for Aircraft is slow and expensive. I think the dual jack was designed and approved before cell phones and media players were common (let alone allowed to be used)

Also, I would bet there was a level of "tech lock-in" ensuring the only source for the headsets were one or two companies.